Sodium Nitroprusside Promotes IRP2 Degradation via an Increase in Intracellular Iron and in the Absence of S Nitrosylation at C178

Wang, Jian; Fillebeen, Carine; Chen, Guohua; Andriopoulos, Bill; Pantopoulos, Kostas

doi:10.1128/mcb.26.5.1948-1954.2006

Cited by 31 publications

(30 citation statements)

References 41 publications

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“…We speculate that the Fe-O-Fe center of FBXL5 may be amenable to redox control and sensitized by oxidative stress. However, our data do not exclude the possibility for alternative pathways that may contribute to the redox control of IRP2 stability, for example involving prolyl-hydroxylases [15,16] or endogenous heme [37][38][39]. Dissection of the molecular pathway underlying the redox regulation of IRP2 awaits further experimentation.…”

Section: Discussionmentioning

confidence: 58%

Redox control of iron regulatory protein 2 stability

2011

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Edited by Stuart Ferguson Keywords:Iron metabolism Iron regulatory protein 2 Proteasome Oxidative stress Hypoxia a b s t r a c t Iron regulatory protein 2 (IRP2) is a critical switch for cellular and systemic iron homeostasis. In iron-deficient or hypoxic cells, IRP2 binds to mRNAs containing iron responsive elements (IREs) and regulates their expression. Iron promotes proteasomal degradation of IRP2 via the F-box protein FBXL5. Here, we explored the effects of oxygen and cellular redox status on IRP2 stability. We show that iron-dependent decay of tetracycline-inducible IRP2 proceeds efficiently under mild hypoxic conditions (3% oxygen) but is compromised in severe hypoxia (0.1% oxygen). A treatment of cells with exogenous H 2 O 2 protects IRP2 against iron and increases its IRE-binding activity. IRP2 is also stabilized during menadione-induced oxidative stress. These data demonstrate that the degradation of IRP2 in iron-replete cells is not only oxygen-dependent but also sensitive to redox perturbations.

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Section: Discussionmentioning

confidence: 58%

Redox control of iron regulatory protein 2 stability

2011

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“…An explanation for the effect of NO has been proposed, suggesting that S-nitrosylation at Cys-178 leads to proteasomedependent IRP2 degradation (17). However, this mechanism, once believed in, was not confirmed by other authors and is still a matter of controversy (35).…”

Section: Discussionmentioning

confidence: 99%

Iron Regulatory Protein 1 Outcompetes Iron Regulatory Protein 2 in Regulating Cellular Iron Homeostasis in Response to Nitric Oxide

Styś

Galy

Starzyński

et al. 2011

Journal of Biological Chemistry

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In mammals, iron regulatory proteins (IRPs) 1 and 2 posttranscriptionally regulate expression of genes involved in iron metabolism, including transferrin receptor 1, the ferritin (Ft) H and L subunits, and ferroportin by binding mRNA motifs called iron responsive elements (IREs). IRP1 is a bifunctional protein that mostly exists in a non-IRE-binding, [4Fe-4S] cluster aconitase form, whereas IRP2, which does not assemble an Fe-S cluster, spontaneously binds IREs. Although both IRPs fulfill a trans-regulatory function, only mice lacking IRP2 misregulate iron metabolism. NO stimulates the IRE-binding activity of IRP1 by targeting its Fe-S cluster. IRP2 has also been reported to sense NO, but the intrinsic function of IRP1 and IRP2 in NOmediated regulation of cellular iron metabolism is controversial. In this study, we exposed bone marrow macrophages from Irp1 ؊/؊ and Irp2 ؊/؊ mice to NO and showed that the generated apo-IRP1 was entirely responsible for the posttranscriptional regulation of transferrin receptor 1, H-Ft, L-Ft, and ferroportin. The powerful action of NO on IRP1 also remedies the defects of iron storage found in IRP2-null bone marrow macrophages by efficiently reducing Ft overexpression. We also found that NOdependent IRP1 activation, resulting in increased iron uptake and reduced iron sequestration and export, maintains enough intracellular iron to fuel the Fe-S cluster biosynthetic pathway for efficient restoration of the citric acid cycle aconitase in mitochondria. Thus, IRP1 is the dominant sensor and transducer of NO for posttranscriptional regulation of iron metabolism and participates in Fe-S cluster repair after exposure to NO.Iron is a cofactor essential for fundamental metabolic processes and is therefore indispensable for cellular function. On the other hand, iron excess is toxic because of the ability of the metal to catalyze the formation of highly reactive hydroxyl radicals. Hence, cellular iron levels and bioavailability must be tightly controlled. Cellular iron homeostasis is coordinately regulated by iron regulatory protein (IRP) 3 1 and 2, which posttranscriptionally modulate the expression of critical iron metabolism genes by interacting with conserved cis-regulatory iron responsive elements (IREs) present in the untranslated region (UTR) of target mRNAs (1). Either of the two IRPs inhibits translation when bound to the single 5Ј UTR IRE of the mRNAs encoding, respectively, the H and L subunits of the iron storage protein ferritin (Ft) and the iron exporter ferroportin (Fpn). IRP binding to the multiple IREs within the 3Ј UTR of the mRNA encoding the transferrin receptor 1 (TfR1) iron uptake molecule prevents its degradation. The IRE-binding activity of both IRPs responds to cellular iron levels, albeit via distinct mechanisms. Under iron-replete conditions, IRP1 assembles an iron-sulfur [4Fe-4S] cluster that precludes IRE binding, and the holo-protein functions as an aconitase. IRP1 is thus bifunctional. IRP2, which is not able to ligate an iron-sulfur cluster, is targeted for prot...

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“…As control, equal volumes of water were added to untreated cells. Exhausted SNP (SNP ex ) was obtained by leaving the solution of SNP under light exposure for 2 days at room temperature as reported previously (Wang et al, 2006). Then, 2 mM SNP or SNP ex was selected for all the experiments because it allowed for evaluation of a reliable degree of apoptosis in a time window of 24 h, and because 2 mM is the concentration close to the EC 50 of the SNP in SH-SY5Y cells.…”

Section: Methodsmentioning

confidence: 99%

“…Although NO is considered the active component of SNP, an increasing number of reports indicate that several SNP-elicited cellular effects are NO-independent Wang et al, 2006). To investigate the genuine mediators of neurotoxic effects triggered by SNP exposure, we treated SH-SY5Y cells, which have been demonstrated previously to be sensitive to NO-induced programmed cell death (Ciriolo et al, 2000), with different concentrations of SNP, ranging from 0.5 to 2 mM.…”

Section: Snp Induces Caspase-dependent Apoptosis In Sh-sy5y Cellsmentioning

confidence: 99%

“…Nevertheless, several in vitro studies revealed that many other biological properties of SNP are independent of the NO moiety because of the huge number of by-products released during its decomposition, such as cyanide, iron, and reactive oxygen species (ROS), which could account predominantly for SNP bioactivity. For example, it has been recently demonstrated that the ability of SNP to induce heme oxygenase-1 expression and iron regulatory protein 2 degradation (Wang et al, 2006) is not tightly dependent on NO release but rather is mediated by the release of its iron moiety. Moreover, it has been demonstrated that hydrogen peroxide production is implicated in SNP-induced cardiomyocyte death (Rabkin and Kong, 2000), and a synergism between NO and the FeCN portion of SNP has been hypothesized to be functional for SNP-induced oligodendrocyte apoptosis (Boullerne et al, 1999).…”

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Reactive Oxygen Species Mediate p53 Activation and Apoptosis Induced by Sodium Nitroprusside in SH-SY5Y Cells

et al. 2008

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Sodium nitroprusside (SNP) is a water-soluble iron nitrosyl complex clinically used as a powerful vasodilator for treatment of hypertension; and, in basic research, it has been used to mainly investigate the cytotoxic effects of nitrosative stress. Although NO is considered a pharmacologically active molecule, not all of the biological effects of SNP are dependent on its NO moiety. To elucidate the molecular executioner(s) responsible for SNP cytotoxicity, this study determines the involvement of oxidative stress in p53 activation and apoptotic induction elicited by SNP in SH-SY5Y neuroblastoma cells. We demonstrate that proapoptotic activity of SNP is independent of NO production, because SNP and its 2-day light-exhausted compound SNP ex trigger apoptosis to the same extent. We provide evidence for the occurrence of oxidative stress and oxidative damage during both SNP and SNP ex exposure and demonstrate that iron-derived reactive oxygen species (ROS) are the genuine mediators of their cytotoxicity. We show that p53 is equally activated upon both SNP and SNP ex treatments. Moreover, as demonstrated by small interfering RNA experiments, we indicate its primary role in the induction of apoptosis, suggesting the ineffectiveness of NO in its engagement. The attenuation of p53 levels, obtained by oxy-radical scavengers, is consistent with the recovery of cell viability and ROS decrease, demonstrate that SNP-mediated p53 activation is an event triggered by ROS and/or ROS-mediated damages. Together, our results suggest that investigations of the physiopathological effects of SNP should consider the role of ROS, other than NO, particularly in some conditions such as apoptotic induction and p53 activation.NO is a diffusible and reactive free radical involved in a wide range of physiological functions, including the control of vascular tone, platelet aggregation, and the immune response (Moncada et al., 1991;Mannick, 2006). In the central nervous system, NO plays a pivotal role as neurotransmitter, neuromodulator, and neuroprotector, even if alteration in its synthesis is detrimental for neuronal cell viability. In fact, during its overproduction, NO acts as a proapoptotic molecule, activating mainly the mitochondrial apoptotic pathway by modulating the expression of apoptosis-associated proteins such as Bax and Bcl-2 (Brü ne, 2005;Pacher et al., 2007). Moreover, sustained production of NO and its reactive nitrogen species (RNS) leads to DNA damage, promoting the activation of the tumor suppressor p53 protein, which in turn can activate transcription of regulatory genes, allowing DNA repair, or programmed cell death (Brü ne and Schneiderhan, 2003;Vousden and Lane, 2007).In general, pathophysiological processes controlled by NO and RNS are investigated by using NO donors with different half-lives, chemical properties, and kinetics of release. One of the most known NO-releasing drugs is the nitroferricyanide

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Sodium Nitroprusside Promotes IRP2 Degradation via an Increase in Intracellular Iron and in the Absence of S Nitrosylation at C178

Cited by 31 publications

References 41 publications

Redox control of iron regulatory protein 2 stability

Redox control of iron regulatory protein 2 stability

Iron Regulatory Protein 1 Outcompetes Iron Regulatory Protein 2 in Regulating Cellular Iron Homeostasis in Response to Nitric Oxide

Reactive Oxygen Species Mediate p53 Activation and Apoptosis Induced by Sodium Nitroprusside in SH-SY5Y Cells

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